I wish Darktide's progression mechanics were as straightforward as the miniatures game

Ordo dockets aren't the same thing as ordo ingots. Ordo dockets, you see, are earned by doing missions, along with the two crafting resources plasteel and diamantine, all three of which you'll need to upgrade your gear at the Shrine of the Omnissiah run by tech-priest Hadron Omega-7-7. New basic gear also costs ordo dockets, but must be bought from Peddler 138/143, the servitor at the Armory Exchange.

Ordo ingots, meanwhile, can only be earned by completing weekly challenges and spent on special gear at Sire Melk's Requisitorium.